Exploring Our Fluid Earth
Teaching Science as Inquiry
Habitat Handout |
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The rocky intertidal is a region of the shore bordered on the seaward side by the reach of ebbing (falling) tides and on the landward side by the reach of flooding (rising) tides. It is essentially the part of the shore that is intermittently awash or exposed as a result of the tide. The boundaries of the intertidal vary with the phase of the moon and with the intensity of wave action, so in practice the region is not defined precisely. The difference between high and low tide in the Hawaiian Islands is generally less than 20 centimeters, but it is meaningful for the distribution of marine organisms on shores where the range is two meters or more. There are fewer species and less diversity on shores where there is a large tidal range, whereas in places with a small tidal range like Hawai‘i, marine plants and animals characteristically arrange themselves to take advantage of conditions of wetness and light. On rocky shores, organisms must be able to retain water and withstand hours of hot sunshine as long as they are wetted occasionally. A tide-pool is small pool of seawater that remains inside rock crevices during periods of low tide.
Corals reefs are shallow ocean habitats found in warm tropical and subtropical waters around the world. Coral reef habitat is formed by living colonies of reef-building cnidarians, called corals. Coral reefs occur in areas with strong wave action as well as in calm lagoons. Although some corals live in deeper water, reef-building corals require bright sunlight in order for the algae that live within their tissue to photosynthesize. Reef-building corals still filter feed—gathering food from the water, but the algae inside their tissues provide additional nutrition, which allows them build hard calcium carbonate reef structures. The reefs that corals build provide shelter for many fishes and invertebrates. Some reef fishes and animals (like the crown of thorns sea star) also feed on coral polyps. Kelp forests are shallow ocean habitats generated by large algae called kelp. These kelp algae grow vertically from rocky seafloors up to the surface and provide shelter and food for a diverse group of marine organisms. Kelp forests are found exclusively in cool, temperate waters. The open ocean or epipelagic zone is the area of the world ocean far away from both the seafloor and all shores. This habitat is characterized by patches of microscopic phytoplankton and zooplankton. Fish predators include seabirds and some large jellyfish. Surface waters face intense sunlight and little structural refuge from predators with the exception of floating debris. Open ocean habitats are found around the world from the cold polar regions to the hot tropics. In the deep water of the ocean, there is massive pressure from the water pushing down from above. The deep sea is also very cold with little or no light. Food is hard to find because the lack of light means that organisms cannot photosynthesize. Thus, there are also fewer organisms in the vast open space. And, there is less habitat structure (no large coral reefs or kelp forests). For these reasons, both food and mates are hard to find. Arctic (near the North Pole) and Antarctic (near the South Pole) waters are very cold. In fact, in the Southern Ocean Basin, water temperatures range from about -2°C to 10°C. The colder temperatures should be cold enough to freeze the water, but salt in the water keeps it from turning to ice. |
Physical feature or form | Description | Adapted function |
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A. Body size and shape | ||
B. Skin color and scales | ||
C. Eyes, jaws, and other head features | ||
D. Mouth and teeth | ||
E. Caudal fin | ||
F. Other fins or appendages |
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G. Behavior |